Publication details
Geometrically Closed Positive Varieties of Star-Free Languages
| Authors | |
|---|---|
| Year of publication | 2020 |
| Type | Article in Proceedings |
| Conference | LATA 2020 |
| MU Faculty or unit | |
| Citation | |
| web | https://link.springer.com/chapter/10.1007%2F978-3-030-40608-0_23 |
| Doi | http://dx.doi.org/10.1007/978-3-030-40608-0_23 |
| Keywords | Language varieties; Geometrical closure; Straubing-Thérien hierarchy; R-trivial monoid |
| Description | A recently introduced operation of geometrical closure on formal languages is investigated. It is proved that the geometrical closure of a language from the positive variety V_3/2, the level 3/2 of the Straubing-Thérien hierarchy of star-free languages, always falls into the variety R_LT, which is a new variety consisting of specific R-trivial languages. As a consequence, each class of regular languages lying between R_LT and V_3/2 is geometrically closed. |
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